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1.
Large volume airgun arrays have been widely used in exploring and monitoring underground structures for nearly a decade. Nowadays, large volume airgun arrays adopt the synchronous excitation mode, and source characteristics are controlled by the source signal of a single airgun, which to some extent limits its application. In order to realize the asynchronous excitation of the airgun array, we developed a new firing system for the airgun array, and carried out a field experiment in the Binchuan Fixed Airgun Signal Transmission station to study the influences of the asynchronous excitation on the source signal. The experimental results show that:the newly developed airgun array firing system can ignite the airguns according to the setting time series with high precision. By designing the excitation time series, the asynchronous excitation can enhance the energy of airgun source signal at 3-5Hz, and reduce the energy of pressure pulse wave at 6-18Hz. The signal detection capability of the asynchronous excitation with time series mode is equivalent to the synchronous excitation. 相似文献
2.
Using an airgun array in a land reservoir as the seismic source for seismotectonic studies in northern China: experiments and preliminary results 总被引：15，自引：0，他引：15
This paper reports the field setup and preliminary results of experiments utilizing an airgun array in a reservoir in north China for a seismotectonic study. Commonly used in offshore petroleum resource exploration, the airgun source was found to be more useful than a traditional explosive source for large‐scale and long offset land seismic surveys. The airgun array, formed by four 1,500 in3 airguns (a total of 6,000 in3 in volume) was placed at a depth of 6–9 m into the reservoir to generate the pressure impulse. No direct evidence was found that the airgun source adversely affected the fish in the reservoir. The peak ground acceleration recorded on the top of the reservoir dam 100 m away was 17.8 gal in the horizontal direction; this is much less than the designed earthquake‐resistance threshold of 125 gal for this dam. The energy for one shot of this airgun array is about 6.68 MJ, equivalent to firing a 1.7 kg explosive. The seismic waves generated by the airgun source were recorded by receivers of the regional seismic networks and a temporary wide‐angle reflection and refraction profile formed by 100 short‐period seismometers with the maximum source‐receiver offset of 206 km. The seismic wave signature at these long‐offset stations is equivalent to that generated by a traditional blast source in a borehole with a 1,000–2,000 kg explosive. Preliminary results showed clear seismic phases from refractions from the multi‐layer crustal structures in the north China region. Forward modelling using numerical simulation confirms that the seismic arrivals are indeed from lower crustal interfaces. The airgun source is efficient, economical, environmentally friendly and suitable for being used in urbanized areas. It has many advantages over an explosive source for seismotectonic studies such as the high repeatability that is supreme for stacking to improve signal qualities. The disadvantage is that the source is limited to existing lakes or reservoirs, which may restrict experimental geometry. 相似文献
3.
Influencing factors of seismic signals generated by un-tuned large volume airgun array in a land reservoir 总被引：7，自引：0，他引：7 
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下载免费PDF全文 Meng Chen Wei Yang Weitao Wang Baoshan Wang Hongkui Ge Li Chen Yansheng Ding Jiyan Qiao Yong Chen 《地震科学（英文版）》2014,27(4):365-376
Un-tuned large volume airgun array in a water reservoir is recently proposed as a new way to generate seismic waves on land. It can be used to explore the earth velocity structure and its temporal variations as well. However, the characteristics of seismic signals (especially far-field signals) from an airgun array in a reservoir and its affecting factors (firing pressure, airgun towing depth, water level of the reservoir, etc.) has not been adequately studied. We analyzed the seismic data collected from field experiments at Binchuan Transmitting Seismic Station in 2011 and 2013 and found that (1) The similarity of seismic signals decrease with distance, which is most likely induced by the decay of signal amplitude and signal to noise ratio (SNR); (2) The amplitudes of far-field airgun signals are almost linearly proportional to the firing pressure; (3) The towing depth of airgun has less effects on the far-field signals; (4) The amplitudes of far-field airgun signals are proportional to the water level of the reservoir. 相似文献
4.
In the design of linear airgun arrays the interaction between the airguns is usually neglected. We review the different formulae which have been proposed for the minimum separation between airguns at which the interaction is negligible. These formulae can all be approximated by a linear function of a single variable. We have analyzed a large number of measurements in order to establish the amount of interaction between two airguns of various volumes at different pressures and depths. The resulting far-field signature has been measured and compared with the sum of the signatures from the two airguns measured in the same experimental situation. The changes in primary pulse amplitude, bubble period and primary/bubble peak-to-peak amplitude ratio were computed from the measurement data as a function of airgun separation, chamber volume, chamber pressure and airgun depth. The influence of a waveshape kit was investigated, and the effects of interaction and the effects of using a waveshape kit were compared. 相似文献
5.
A marine source generates both a direct wavefield and a ghost wavefield. This is caused by the strong surface reflectivity, resulting in a blended source array, the blending process being natural. The two unblended response wavefields correspond to the real source at the actual location below the water level and to the ghost source at the mirrored location above the water level. As a consequence, deghosting becomes deblending (‘echo‐deblending’) and can be carried out with a deblending algorithm. In this paper we present source deghosting by an iterative deblending algorithm that properly includes the angle dependence of the ghost: It represents a closed‐loop, non‐causal solution. The proposed echo‐deblending algorithm is also applied to the detector deghosting problem. The detector cable may be slanted, and shot records may be generated by blended source arrays, the blending being created by simultaneous sources. Similar to surface‐related multiple elimination the method is independent of the complexity of the subsurface; only what happens at and near the surface is relevant. This means that the actual sea state may cause the reflection coefficient to become frequency dependent, and the water velocity may not be constant due to temporal and lateral variations in the pressure, temperature, and salinity. As a consequence, we propose that estimation of the actual ghost model should be part of the echo‐deblending algorithm. This is particularly true for source deghosting, where interaction of the source wavefield with the surface may be far from linear. The echo‐deblending theory also shows how multi‐level source acquisition and multi‐level streamer acquisition can be numerically simulated from standard acquisition data. The simulated multi‐level measurements increase the performance of the echo‐deblending process. The output of the echo‐deblending algorithm on the source side consists of two ghost‐free records: one generated by the real source at the actual location below the water level and one generated by the ghost source at the mirrored location above the water level. If we apply our algorithm at the detector side as well, we end up with four ghost‐free shot records. All these records are input to migration. Finally, we demonstrate that the proposed echo‐deblending algorithm is robust for background noise. 相似文献
6.
Far-field signatures from an airgun array are usually obtained by carrying out extensive field measurements. In order to decrease the need for such measurements, we have developed a method for computing signatures from linear airgun arrays where the distances between the airguns are such that the non-linear interaction among the airguns is negligible. The signature from a single airgun of a given type is computed from the following airgun parameters: airgun chamber volume, chamber pressure, airgun depth and position of the waveshape plate within the chamber. For calibration purposes, a recorded signature for one set of airgun parameters has to be provided for each type of airgun. The signatures are computed by using empirical relations between signature properties and the airgun parameters, and by treating the primary and bubble pulses separately. The far-field signature from a linear airgun array can now be computed by summation of the delayed signatures from the airguns in the array. Practical results are shown for an array with different PAR (Bolt) 1500 C airguns. 相似文献
7.
The relative merits of a 48-gun, 9324 cu. in. (153 litre) airgun array and a 200 kg explosive source are considered for the purposes of long-range (0–400 km) refraction seismic work, with particular reference to traveltime modelling. Theoretical source calculations indicate that in the frequency range 2.5–12.0 Hz, the airgun source will produce an RMS pressure ∼ 8% of that produced by the explosive source and an initial burst pressure ∼17% of that produced by the explosive source. Observed data support these calculations at short ranges and illustrate the greater attenuation of the airgun signal with range due to its lack of very low frequency (< 5 Hz) content. At short offsets, the airgun array provides a preferable seismic source to the explosives, due to densely spaced shots and a consistent waveform resulting in excellent trace-to-trace coherence. With increasing offsets, it may be necessary to stack the airgun data to enhance its signal-to-noise ratio: here we use a 4-fold stack. Large explosive shots, although more powerful, produce a less consistent waveform and are more widely spaced due to operational constraints. The offset at which airguns provide a preferable source is dependent on the ambient noise. This practical comparison of real sources demonstrates that, even without advanced processing, a well-tuned airgun array may provide a preferable source to explosives at offsets up to 160 km, under favourable experimental conditions. 相似文献
8.
M. H. SAFAR 《Geophysical Prospecting》1983,31(2):343-350
Recently the author developed and demonstrated (Safar 1980) an efficient method for operating the airgun. The method involves the generation of a short seismic pulse from the pressure bubble pulses radiated by an airgun when fired several times at the same optimum depth but with different chamber pressures. The purpose of this paper is to present and discuss the test results obtained when implementing the same method using a two-dimensional airgun array. The array consists of seven 0.65 liter airguns fired simultaneously at the same depth but with different chamber pressures. It is shown that the far-field pressure pulse radiated by the seven 0.65 liter airgun array is similar to that radiated by the Flexichoc seismic source. It is concluded that the proposed airgun array can be used as a subarray to form an extremely powerful super-long array suitable for deep seismic exploration. The author would like to thank the Chairman and Board of Directors of the British Petroleum Co. Ltd for permission to publish this paper. Thanks are also due to Mike Symes and Lovell Cox for carrying out the field tests and Seismograph Service (England) Ltd for providing the airguns. 相似文献
9.
大容量气枪震源子波时频特性及其影响因素 总被引：3，自引：3，他引：0
通过分析福建街面水库气枪实验的近场水听器记录,研究气枪子波时频特性及其受沉放深度和工作压力的影响,并结合气泡模型解释气泡振荡过程。数据分析表明：①气枪子波由主脉冲和气泡脉冲组成。主脉冲振幅大,持时短,频带宽,通常应用于浅部探测;气泡脉冲能量集中在低频段,垂直穿透深,水平传播远,通常应用于深部探测。②随沉放深度的增加,主脉冲振幅变化很小,气泡脉冲振幅增加,初泡比减小,气泡周期减小,低频段主频增加。沉放深度为10m时,主脉冲振幅和初泡比最大,可应用于浅部探测;沉放深度为25m时,气泡脉冲振幅很大,初泡比最小,可应用于深部探测。③工作压力增加时,主脉冲振幅、气泡脉冲振幅、初泡比、气泡周期等随之增大,低频段主频则减小。 相似文献
10.
A.M. ZIOLKOWSKI 《Geophysical Prospecting》1980,28(6):902-918
A seismic source array is normally composed of elements spaced at distances less than a wavelength while the overall dimensions of the array are normally of the order of a wavelength. Consequently, unpredictable interaction effects occur between element and the shape of the far field wavelet, which is azimuth-dependent, can only be determined by measurements in the far field. Since such measurements are very often impossible to make, the shape of the wavelet—particularly its phase spectrum—is unknown. A theoretical design method for overcoming this problem is presented using two scaled arrays. The far field source wavelets from the source arrays have the same azimuth dependence at scaled frequencies, and the far field wavelets along any azimuth are related by a simple scaling law. Two independent seismograms are generated by the two scaled arrays for each pair of source-receiver locations, the source wavelets being related by the scaling law. The technique thus permits the far field waveform of an array to be determined in situations where it is impossible to measure it. Furthermore it permits the array design criteria to be changed: instead of sacrificing useful signal energy for the sake of the phase spectrum, the array may be designed to produce a wavelet with desired amplitude characteristics, without much regard for phase. 相似文献
11.
Characteristics of the Seismic Waves from a New Active Source Based on Methane Gaseous Detonation 总被引：1，自引：0，他引：1
WANG Weitao WANG Xiang MENG Chuanmin DONG Shi WANG Zhigang XIE Junju WANG Baoshan YANG Wei XU Shanhui WANG Tao 《中国地震研究》2019,33(2):354-366
Active seismic sources are critical for obtaining high resolution images of the subsurface. For active imaging in urban areas, environment friendly and green seismic sources are required. In present work, we introduce a new type of green active source based on the gaseous detonation of methane and oxygen. When fired in a closed container, the chemical reaction, i.e. gaseous detonation, will produce high pressure air over 150MPa. Seismic waves are produced when high pressure air is quickly released to impact the surroundings. The first field experiment of this active source was carried out in December, 2017 in Jingdezhen, Jiangxi Province, where a series of active sources were excited to explore their potential in mine exploration. In current work, we analyzed the seismic waves recorded by near-field accelerators and a dense short-period seismic array and compared them with those from a mobile airgun source, another kind of active source by releasing high pressure air into water. The results demonstrate that it can be used for high resolution near surface imaging. Firstly, the gaseous detonation productions are harmless CO2 and water, making it a green explosive source. Secondly, the dominant seismic frequencies are 10-80Hz and a single shot can be recorded up to 15km, making it suitable for local structure investigations. Thirdly, it can be excited in vertical wells, similar to traditional powder explosive sources. It can also act as an additional on-land active source to airgun sources, which requires a suitable water body as intermediate media to generate repeating signals. Moreover, the short duration and high frequency signature of the source signals make it safe with no damage to nearby buildings. These make it convenient to excite in urban areas. As a new explosive source, the excitation equipment and conditions, such as gas ratio, sink depth and air-releasing directions, need further investigation to improve seismic wave generation efficiency. 相似文献
12.
R. C. JOHNSTON 《Geophysical Prospecting》1982,30(6):752-773
Source strength of an airgun array may be increased by:
- — utilizing higher pressure,
- — increasing total array volume,
- — employing more guns,
- — improving gun efficiency.
- — shuttle motion,
- — bubble pressure,
- — chamber pressure,
- — bubble radius.
13.
为研究震源和水听器电缆沉放深度对单道地震勘探的影响,建立鬼波影响模型,采用雷克子波模拟震源子波,分析因震源及水听器电缆沉放深度产生的鬼波对一次有效反射地震波的影响,并采用不同震源和水听器电缆沉放深度的数据对本次研究结论进行验证。研究表明：地震剖面分辨率和震源及水听器电缆沉放的总深度呈反比;随着震源或水听器电缆沉放深度的增加,地震剖面的分辨率递减,接收地震波能量从低值递增到最大值,再从最大值缓慢降低到稳定值;当水听器电缆沉放深度小于168.8/f(m)时,接收地震波能量随震源沉放深度变化的波动相对平缓,水听器电缆沉放深度浅有利于地震波的一致性,但沉放深度过浅时接收地震波能量将被极大削弱,会明显降低地震波的有效穿透深度;当震源沉放深度约为292.3/f(m)时,一次有效反射波的峰值和震源鬼波的峰值重叠,接收地震波能量最大;当震源沉放深度大于584.6/f(m)时,不考虑地震波能量在水中衰减的情况下,震源沉放深度继续增加对接收地震波能量的增加无效。 相似文献
14.
Experiments in an 850 litre water tank were performed in order to study temperature effects on airgun signatures, and to achieve a better understanding of the physical processes that influence an airgun signature. The source was a bolt airgun with a chamber volume of 1.6 cu.in. The pressure used was 100 bar and the gun depth was 0.5 m. The water temperature in the tank was varied between 5°C and 45°C. Near-field signatures were recorded at different water temperatures. Typical signature characteristics such as the primary-to-bubble ratio and the bubble time period increased with increasing water temperature. For comparison and in order to check whether this is valid for larger guns, computer modelling of airguns with chamber volumes of 1.6 and 40 cu.in. was performed. In the modelling the same behaviour of the signatures with increasing water temperature can be observed. The increase in the primary-to-bubble ratio and the bubble time period with increasing water temperature can be explained by an increased mass transfer across the bubble wall. 相似文献
15.
《中国科学:地球科学(英文版)》2017,(10)
The active sources generate seismic waves transmitting appropriate through the deep is underground key and can be used to image Abstract high-resolution subsurface structures.Therefore,an seismic source the factor to active source exploration.In order to study the structure of continental crust and its temporal variations,we selected an artificial seismic source generated from releasing air bubbles in water(airgun source hereinafter)out of a variety and of artificial sources like the is explosion,new electronic sparkers,source hammering,eccentric proven vibration,be heavy-duty train vibration,vibroseis etc.Airgun Three source Fixed a type of artificial that have been to environmentally friendly,safe,and highly efficient.Airgun western Signal China Transmission and Stations(FASTS)have been for built a few years ago in Yunnan,Xinjiang,and Gansu provinces in have been continuously them running several years.Seismic waves generated away by the the airgun sources are highly seismic reproducible waves and stacking in of can produce can good seismograms on 1300 stations km far from source,for instance,an produced Xinjiang FASTS be well about recorded 60 nearly away after 5000 stacking,China covering area of 6 million km2 and penetrating down to of a depth of km.Establishing about 10 FASTSs in would enable long-term illuminate continuous subsurface underground structures,monitoring can all 9.6 million km2 of land area.Treating from airgun sky active sources as lanterns to we achieve the situation with"Beidou surveys the and lantern illuminates underground". 相似文献
16.
安徽气枪实验固定台层析成像初步结果 总被引：3，自引：2，他引：1
为探索气枪震源在探测区域性地壳结构中的应用, 2015年10月10～20日在长江马鞍山-安庆段开展气枪流动激发实验（安徽实验）,在20个固定点定点激发2973炮,中间流动激发1872炮,由周边109个固定台、700个流动台（包括11条测线）进行接收。为获取郯庐断裂带南端较为精细的地壳速度结构,本文利用安徽气枪实验中采集到的固定台数据进行初至P波震相拾取,对20个气枪源、52个台站、335个震相进行体波层析成像,验证了利用气枪震源进行体波层析成像的可行性,并得到了P波速度结构的一些初步结果：①利用大容量气枪震源可进行三维体波层析成像;②15km深度的成像结果显示出大区域高低速异常区的清晰轮廓,即从研究区中心向外整体呈现出低-超低-低-高的分布特征,与地质构造背景相关,具有显著的横向不均匀性;③秦岭-大别造山带显示出高速异常,与其深部超高压变质岩相对应,而长江中下游地区整体呈现低速异常,与其特殊的成矿背景相对应。 相似文献
17.
This paper studies aspects that influence the de‐ghosting performance of marine multi‐level sources based on a modified Johnson model. The normalized squared error between actual signature and its corresponding ghost‐free signature is introduced to evaluate the multi‐level source design. The results show that optimum depth combinations and volume combinations exist in the design. However, there is also some flexibility in the volume combination which makes it possible to optimize with respect to residual bubble oscillation. By considering both operational aspects and performance, we propose that three or four levels in a multi‐level source are reasonable. Compared to a horizontal source, a multi‐level source can be designed to reduce the notch effect, strengthen the down‐going energy and improve the energy transmission directivity. Studies of the influence of depth and firing time deviations indicate that a multi‐level source is more stable than a normal horizontal source in an operational environment. 相似文献
18.
Regional Scale Seismological Investigation on the Continent Crust Using Airgun Sources——A Perspective Review 总被引：1，自引：1，他引：0
The investigations on the structure and temporal variations of the continent crust have been the long-lasting topics of seismology. The artificial sources play the most important role in these studies for their well-known locations and occur times among all the sources producing elastic waves, so that precise results are obtained. In past decades, we have successfully excited the airgun sources in on-land water bodies such as reservoirs, expanding their applications in marine seismology. Large volume airguns have been used to produce low frequency signals which can travel hundreds of kilometers after stacking, providing a source connecting the exploration seismology and traditional seismology at regional scale. In this review, we introduce the changes through which we turn the airgun into scientific instruments by experiments. We also present the advances on imaging the continental crust structure and monitoring the velocity variations using the highly repeatable signals emitted by airgun sources. The potential applications such as imaging the subsurface of urban areas and high resolution illuminating of mines are proposed and the challenges for further investigations are also discussed. 相似文献
19.
GUO Yang XU Jiajun LIN Chen JIN Xing YAO Huajian YANG Hongfeng CAI Huiteng 《中国地震研究》2019,33(2):265-275
112 short-period seismographs were set up in the 400km2 area of Pingtan Island and its surrounding areas in Fujian. The combined observations of the airgun source and ambient noise source were carried out using a dense array to receive the 387 airgun signals excited around the island and one month of continuous ambient noise recording. The 1-D P-wave and S-wave shallow velocity model of Pingtan Island is obtained by the inversion of the airgun body wave''s first arrival time data, and the reliability of the velocity model is verified by using the surface wave phase velocity dispersion curve, which can provide initial model for subsequent 3-D imaging. The experimental results show that this experiment is a successful demonstration of local scale green non-destructive detection, which can provide basic data for shallow surface structure research and strong vibration simulation of the Pingtan Island. 相似文献
20.
利用固定台站分析长江激发气枪信号特征 总被引：1，自引：1，他引：0
“地学长江计划”安徽实验是以气枪震源为核心的大型主动源探测实验。通过在长江安徽段20个固定点定点激发气枪震源,结合109个固定台站、11条流动测线组成的观测网络,首次利用主动源实现了对长江流域安徽段约6万km2面积的三维地下结构探测。本文利用固定台站对长江激发气枪信号进行了分析,结果表明,长江中气枪信号激发效果良好,固定台记录中气枪信号可识别的最远距离达300km。对气枪信号绝对振幅的研究结果表明：① 50km处的气枪信号约为10nm量级,200km处的气枪信号小于1 nm;② 气枪信号强度的空间分布存在一定的方位各向异性,可能与长江的几何形状有关;③ 台站背景噪声对于提取气枪信号至关重要,高质量的固定台网为识别nm量级气枪信号提供了可能。 相似文献